Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended
	Nov. 30, 2015	Nov. 30, 2014
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	$ 9,383,000	$ 9,058,000
Interest costs	7,693,000	7,014,000
Expected return on assets	(12,014,000)	(12,438,000)
Prior service cost (credit) amortization	402,000	407,000
Actuarial loss (gain) amortization	4,754,000	4,901,000
Periodic benefit costs, net	10,218,000	8,942,000
Defined Benefit Plan, Contributions by Employer	0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	259,000	225,000
Interest costs	352,000	352,000
Expected return on assets	0	0
Prior service cost (credit) amortization	57,000	57,000
Actuarial loss (gain) amortization	173,000	261,000
Periodic benefit costs, net	841,000	895,000
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	353,000	472,000
Interest costs	427,000	415,000
Expected return on assets	0	0
Prior service cost (credit) amortization	(30,000)	(30,000)
Actuarial loss (gain) amortization	(116,000)	(105,000)
Periodic benefit costs, net	$ 634,000	$ 752,000